A generation of change-makers is showing the world just how powerful a tweet can be.

Sit-ins, marches, picket signs—these are the images we conjure up when we think of activism in the traditional sense, but for teens and twenty-somethings, change is starting with the click of a mouse.

With an estimated two in five young adults engaging with social issues online, we've entered into the age of digital activism, where grassroots movements are created through tweets, reblogs, likes, and status updates. Though some critics derisively refer to it as "slacktivism," this new wave is proving how logging on can seriously impact your community—and the world.

"I had always been interested in women's rights, but I didn't consider myself an activist until I joined Tumblr four years ago," says college freshman Melissa Hudson, whose activism relates to sexual assault, reproductive rights, and LGBTQ issues. "I didn't intend to be part of this community when I signed up for the site, but I found myself drawn to posts about gender biases and links to stories about girls who were denied proper contraceptive care. There was a dialogue online about stuff that no one I knew in real life was talking about, and the more I read, the more I realized it wasn't just a conversation. There were petitions being signed, protests being held on blogs, memes and photo series being created, and they all meant something."

Victoria Snow, the blogger who runs the Tumblr Feminish, agrees: "I can honestly say I wouldn't be the feminist I am today without the internet." The goal of her blog is to offer a place for safe and open discussions on feminist issues; she also uses social media to launch and support petitions, including one in support of the recent upskirting ban in Massachusetts. Despite the success of the bill, which makes the act of photographing or recording under someone's clothing a punishable crime, Victoria acknowledges that there's a persistent misconception that digital activism is ineffective. "A lot of impact can be made online, and older generations don't always get that," she says. "They see us on our phones or laptops and think who knows what. But we're organizing, we're creating, we're signal-boosting, we're creating awareness. We're changing the world."

This trend was not borne out of convenience, but rather a genuine faith in the power of the internet. According to a study by the Intelligence Group, two out of three Millennials believe that "a person on a computer, being aware and spreading the word" is capable of sparking more change than "a person on the street, rallying and protesting." For Melissa, online activism is indeed the most compelling way to inspire widespread social change: "A lot of physical protests and movements are very localized, but online there are no limits to who can engage with you."

And since many activists lack access to traditional outlets like network television, social media platforms like Twitter and Facebook have become powerful forums for first-hand accounts and live reports of situations around the world. As Jim Loughran, head of media and communications for human rights group Front Line Defenders, explains, "Social media enables us to maintain a support and contact base in almost every country in the world. It no longer matters whether you are based in Dublin or Doha. We're connected by a community of interest, not geography."

While this is awesome, it can also be overwhelming, which is why some organizations are working to link up teens with causes and strategies. Take DoSomething.org, a non-profit specifically created to empower a generation who wants to, well, do something. The majority of its 2.5 million members are between the ages of 13 and 25—the rest are lovingly referred to as "old people" on the site. "A lot of teens don't know where to start," explains Colleen Wormsley, a marketing associate at DoSomething. "We show them different ways to take action in hopes that it will be a lifelong habit." The site's members engage with their causes by participating in Snapchat selfie challenges and Twitter debates, and by using text messaging to do everything from raising awareness against bullying to preventing teen pregnancy.

But for many activists abroad, social media can also carry great personal risks. Maryam al-Khawaja is a Bahraini activist who became a global figure when she used digital platforms to document the uprising in her country. She calls the online tools "a double-edged sword": Though they expand the opportunity for real-time coverage of human rights issues—which is vital in countries like Bahrain where the media is state-controlled—advanced technology also makes activists vulnerable to attack both online and off.

"What's amazing about Twitter," she says, "is that I write 140 characters, and it reaches hundreds of thousands of people across the globe, including journalists, policymakers and international NGOs. At the same time, Twitter is the place where I've received countless death and rape threats, plus the regime has learned to use these mediums as much as we activists have."

Even in the States, social media is not without its dangers for those pursuing change. Victoria, the Feminish founder, uses an alias as a way to protect her personal information. Despite taking precautions early on in her activism work, she's received rape and death threats just like Maryam, with some cyber-harassers messaging her home address to her, claiming they'll stalk and reenact her past sexual assault.

It should come as no surprise that these girls haven't allowed threats to stop them, however. Now in self-enforced exile due to warnings of arrest as well as continued intimidation, Maryam continues her work as the acting president of the Bahrain Center for Human Rights and encourages young people everywhere to do whatever they can to help others: "Every night before you go to sleep, ask yourself, 'What did I do today to try and make this world a better place?'" Sometimes it really is as simple—and powerful—as sending a tweet.